(19)
(11) EP 0 479 618 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
03.11.1993 Bulletin 1993/44

(43) Date of publication A2:
08.04.1992 Bulletin 1992/15

(21) Application number: 91309143.5

(22) Date of filing: 04.10.1991
(51) International Patent Classification (IPC)5: G06F 15/68
(84) Designated Contracting States:
DE NL

(30) Priority: 05.10.1990 US 593659

(71) Applicant: KABUSHIKI KAISHA TOSHIBA
Kawasaki-shi, Kanagawa-ken 210 (JP)

(72) Inventors:
  • Silver,Michael D.
    Illinois 60062 (US)
  • Judd,Thomas C.
    Illinois 60076 (US)

(74) Representative: BATCHELLOR, KIRK & CO. 
2 Pear Tree Court Farringdon Road
London EC1R 0DS
London EC1R 0DS (GB)


(56) References cited: : 
   
       


    (54) A method and apparatus for calibrating magnetic and geometrical distortions in an imaging system


    (57) A method and apparatus to calibrate and correct magnetic and geometrical distortions in an imaging system, specifically a computer tomography (CT) system, includes a calibration object which is placed on the surface of an image intensifier. An image frame of the calibration object is generated, and a vertical correction table is generated corresponding to the amount of image distortion caused to the image frame of the calibration object. The image frame is corrected using the vertical correction table, and the corrected image frame data is summed or averaged and either stored for further transformation into a slice image or used to generate a horizontal correction table to correct distortions in the horizontal direction. Once the vertical and horizontal correction tables have been generated using the calibration object, subsequent image frames are corrected using the correction values in the correction tables.






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